[PATCH v6 08/17] static_call: Avoid kprobes on inline static_call()s

[Peter Zijlstra <peterz@infradead.org>]

Similar to how we disallow kprobes on any other dynamic text
(ftrace/jump_label) also disallow kprobes on inline static_call()s.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 arch/x86/kernel/kprobes/opt.c |    4 +-
 include/linux/static_call.h   |   11 +++++++
 kernel/kprobes.c              |    2 +
 kernel/static_call.c          |   64 ++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 80 insertions(+), 1 deletion(-)

--- a/arch/x86/kernel/kprobes/opt.c
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -17,6 +17,7 @@
 #include <linux/ftrace.h>
 #include <linux/frame.h>
 #include <linux/pgtable.h>
+#include <linux/static_call.h>
 
 #include <asm/text-patching.h>
 #include <asm/cacheflush.h>
@@ -209,7 +210,8 @@ static int copy_optimized_instructions(u
 	/* Check whether the address range is reserved */
 	if (ftrace_text_reserved(src, src + len - 1) ||
 	    alternatives_text_reserved(src, src + len - 1) ||
-	    jump_label_text_reserved(src, src + len - 1))
+	    jump_label_text_reserved(src, src + len - 1) ||
+	    static_call_text_reserved(src, src + len - 1))
 		return -EBUSY;
 
 	return len;
--- a/include/linux/static_call.h
+++ b/include/linux/static_call.h
@@ -110,6 +110,7 @@ struct static_call_key {
 
 extern void __static_call_update(struct static_call_key *key, void *tramp, void *func);
 extern int static_call_mod_init(struct module *mod);
+extern int static_call_text_reserved(void *start, void *end);
 
 #define DEFINE_STATIC_CALL(name, _func)					\
 	DECLARE_STATIC_CALL(name, _func);				\
@@ -153,6 +154,11 @@ void __static_call_update(struct static_
 	cpus_read_unlock();
 }
 
+static inline int static_call_text_reserved(void *start, void *end)
+{
+	return 0;
+}
+
 #define EXPORT_STATIC_CALL(name)					\
 	EXPORT_SYMBOL(STATIC_CALL_KEY(name));				\
 	EXPORT_SYMBOL(STATIC_CALL_TRAMP(name))
@@ -182,6 +188,11 @@ void __static_call_update(struct static_
 	WRITE_ONCE(key->func, func);
 }
 
+static inline int static_call_text_reserved(void *start, void *end)
+{
+	return 0;
+}
+
 #define EXPORT_STATIC_CALL(name)	EXPORT_SYMBOL(STATIC_CALL_KEY(name))
 #define EXPORT_STATIC_CALL_GPL(name)	EXPORT_SYMBOL_GPL(STATIC_CALL_KEY(name))
 
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -35,6 +35,7 @@
 #include <linux/ftrace.h>
 #include <linux/cpu.h>
 #include <linux/jump_label.h>
+#include <linux/static_call.h>
 
 #include <asm/sections.h>
 #include <asm/cacheflush.h>
@@ -1591,6 +1592,7 @@ static int check_kprobe_address_safe(str
 	if (!kernel_text_address((unsigned long) p->addr) ||
 	    within_kprobe_blacklist((unsigned long) p->addr) ||
 	    jump_label_text_reserved(p->addr, p->addr) ||
+	    static_call_text_reserved(p->addr, p->addr) ||
 	    find_bug((unsigned long)p->addr)) {
 		ret = -EINVAL;
 		goto out;
--- a/kernel/static_call.c
+++ b/kernel/static_call.c
@@ -204,8 +204,58 @@ static int __static_call_init(struct mod
 	return 0;
 }
 
+static int addr_conflict(struct static_call_site *site, void *start, void *end)
+{
+	unsigned long addr = (unsigned long)static_call_addr(site);
+
+	if (addr <= (unsigned long)end &&
+	    addr + CALL_INSN_SIZE > (unsigned long)start)
+		return 1;
+
+	return 0;
+}
+
+static int __static_call_text_reserved(struct static_call_site *iter_start,
+				       struct static_call_site *iter_stop,
+				       void *start, void *end)
+{
+	struct static_call_site *iter = iter_start;
+
+	while (iter < iter_stop) {
+		if (addr_conflict(iter, start, end))
+			return 1;
+		iter++;
+	}
+
+	return 0;
+}
+
 #ifdef CONFIG_MODULES
 
+static int __static_call_mod_text_reserved(void *start, void *end)
+{
+	struct module *mod;
+	int ret;
+
+	preempt_disable();
+	mod = __module_text_address((unsigned long)start);
+	WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
+	if (!try_module_get(mod))
+		mod = NULL;
+	preempt_enable();
+
+	if (!mod)
+		return 0;
+
+	ret = __static_call_text_reserved(mod->static_call_sites,
+			mod->static_call_sites + mod->num_static_call_sites,
+			start, end);
+
+	module_put(mod);
+
+	return ret;
+}
+
 static int static_call_add_module(struct module *mod)
 {
 	return __static_call_init(mod, mod->static_call_sites,
@@ -275,6 +325,20 @@ static struct notifier_block static_call
 
 #endif /* CONFIG_MODULES */
 
+int static_call_text_reserved(void *start, void *end)
+{
+	int ret = __static_call_text_reserved(__start_static_call_sites,
+			__stop_static_call_sites, start, end);
+
+	if (ret)
+		return ret;
+
+#ifdef CONFIG_MODULES
+	ret = __static_call_mod_text_reserved(start, end);
+#endif
+	return ret;
+}
+
 static void __init static_call_init(void)
 {
 	int ret;